TYPES OF DAMP

INTRODUCTION

Damp (ness) is the presence of unwanted moisture in the structure of a building, either the result of intrusion from outside or condensation from within the structure.

TYPES OF DAMP

1. Penetrating Damps

When water penetrate become trapped in the structure .all structure

2. Rising Damps

This occurs when the structure sucks moisture out of the ground. Old structure without a damp proof course (DPC) and damp membrane are especially vulnerable AND BLOCK WALL also tends to become more porous age.

Hygroscopic Damp occurs when the structure absorb moisture from the atmosphere, it is rare than other types, but may be present at the same times as them.

 Symptoms

• Stained or peeling wall paper
• Salt deposit (efflorescence) on painted or bare plaster wall
• Swollen or blistered painted wood work
• Black mould in badly ventilated are or behind furniture

Effect

• Strength i.e. adhesion of finishes e.g. paint, wall covering are affected
• Size change-increased due to moisture content shrinkage drying
• Chemical action likely chemical attack on building material e.g. paint
• Biological action, exposure to weather likely to affect durability of material
• Decay i.e. Wet not require 40-5-% moisture content
• Metal corrosion-change in size
• Electric Shock-structural defect due to subsidence.